All MBTA mass transit was shut down as well as all commuter rail coming into and leaving Boston. However, WBUR-FM reports that Logan Airport remains open but under heightened security.

At least a quarter of a million people live in those suburbs. Many people in the city of Boston and surrounding areas rely on the Massachusetts Bay Transit Authority to get to work.

The announcement Friday morning comes hours after the killing of one suspect, known as the man in the black hat from marathon surveillance footage. The man in the white hat is on the loose and police are calling him a "terrorist" who came here "to kill."